UNIT-I

Environment and its significance

 Environment: Definition
The environment refers to the surroundings or external conditions in which an organism
lives, grows, develops, and interacts. It includes all living (biotic) and non-living (abiotic)
things that influence life on Earth.

In simple terms:
"Environment is everything that surrounds us and affects our ability to live on Earth –
including air, water, land, plants, animals, and human-made structures."

Components of the Environment:

The environment is made up of two main components:

🔹 Biotic Components (Living)

All living organisms:

 Plants
 Animals
 Microorganisms (bacteria, fungi, algae)
 Humans

These interact with each other in ecosystems through food chains, reproduction, and survival.

🔹 Abiotic Components (Non-living)

Physical and chemical elements:

 Air
 Water
 Soil
 Sunlight
 Temperature
 Minerals

These provide the basic conditions for life to exist and thrive.

Types of Environment:

🔹 Natural Environment:

 Formed by nature without human intervention.

 Examples: Forests, mountains, rivers, oceans, deserts, wildlife.
  Includes ecosystems like: Terrestrial (land-based) , Aquatic (water-based)

🔹 Artificial / Built Environment:

 Created and modified by humans.

 Examples: Cities, buildings, roads, dams, industries.
 Often disrupts natural ecosystems

 Significance of the Environment

1. Provides Essential Resources (Air, Water, Food, Shelter, and Energy)

The environment supplies basic necessities of life to all organisms:

 Air: Provides oxygen for respiration in animals and humans, and carbon dioxide for
photosynthesis in plants.
 Water: Vital for drinking, irrigation, industrial use, and biological functions in
organisms.
 Food: Comes from plants (agriculture), animals (livestock, fish), and natural
ecosystems (forests, oceans).
 Shelter: Natural habitats like forests, caves, and trees offer protection and living space
for wildlife; humans use natural materials (wood, stone) to build homes.
 Energy: The environment offers both renewable (solar, wind, hydro) and non-
renewable (coal, oil, gas) energy sources for heating, cooking, electricity, and
transportation.

2. Maintains a Balance in Natural Ecosystems (e.g., Oxygen–Carbon

Dioxide Cycle)

The environment naturally regulates essential biogeochemical cycles:

 Oxygen–Carbon Dioxide Cycle: Plants take in carbon dioxide during

photosynthesis and release oxygen. Animals and humans take in oxygen during
respiration and release carbon dioxide. This maintains a balanced level of gases in the
atmosphere.
 Other important cycles: Nitrogen Cycle Helps plants grow by converting
nitrogen into usable forms. Water Cycle Maintains water availability through
evaporation, condensation, and precipitation.

3. Supports Life Processes and Biodiversity

 The environment provides the right conditions for organisms to carry out their life
processes, such as: Respiration, reproduction, growth, and nutrition.
 Biodiversity: Refers to the variety of life forms (plants, animals, microorganisms)
found in an ecosystem. Biodiversity increases ecosystem stability and resilience.
Every species plays a role in maintaining the ecological balance, like pollination,
seed dispersal, and pest control.

4. Influences Climate, Weather, Health, and Economic Activities

  Climate and Weather: Environmental factors like oceans, forests, and atmosphere
influence temperature, rainfall, wind patterns, and seasons.
 Health: Clean air, safe drinking water, and a healthy ecosystem help prevent diseases.
Pollution or degradation can cause respiratory diseases, waterborne illnesses, etc.
 Economic Activities: Agriculture, fishing, forestry, mining, and tourism are directly
dependent on environmental conditions. Degradation of the environment can reduce
productivity and increase disaster risks (floods, droughts).

5. Helps in Recycling Nutrients and Decomposing Waste Through Natural

Cycles

 Decomposers (bacteria, fungi, insects) break down dead plants and animals into
simple nutrients, which are returned to the soil for use by plants.
 These nutrient cycles (carbon, nitrogen, phosphorus) are essential for: Soil fertility,
Plant growth, Clean air and water
 Natural waste management: The environment has built-in processes for recycling
organic waste, filtering water through wetlands, and purifying air through trees.

Habitat and Ecological Niche

 Habitat: Habitat – Where an organism lives

A habitat is the natural environment in which a particular organism lives, grows, and
reproduces. It includes everything the organism needs to survive—food, water, shelter, and
space.

Types of Habitats:

1. Terrestrial habitats – found on land

Examples: forests, deserts, grasslands, mountains
2. Aquatic habitats – found in water
Examples: oceans, rivers, lakes, ponds

Examples:

 A frog lives in a pond. It depends on water for laying eggs, hunting insects, and
keeping its skin moist.
 A tiger lives in a forest, which provides it with prey (like deer), cover for hunting,
and space for roaming.

Ecological Niche:

Definition:

An ecological niche is the role or function of an organism in its environment.

It includes everything about how the organism lives and survives in its habitat. A niche is
like a complete biography of an organism’s lifestyle in nature:

 What it eats
  When it eats
 Where it lives
 How it survives
 How it interacts with others

Every species has its unique niche, and this is what keeps ecosystems diverse and
functioning.

Key Components of a Niche:

An organism’s niche includes:

1. Habitat – Where it lives

Example: A rabbit lives in grasslands.
2. Food – What it eats and how it gets food
Example: The rabbit eats grass and herbs.
3. Predators – What eats it
Example: Foxes or eagles may eat the rabbit.
4. Activity Pattern – When it is active (diurnal/nocturnal)
Example: Rabbits are mostly active at dawn and dusk.
5. Reproductive Behaviour – How it reproduces
Example: Rabbits reproduce quickly to maintain their population.
6. Interactions with Other Species – Competition, cooperation, symbiosis, etc.
Example: Rabbits compete with other herbivores for grass.

Example 1: Bee’s Niche

Let’s take the example of a bee.

 Habitat: Gardens, meadows, forests

 Food: Collects nectar and pollen from flowers
 Role: Pollinates flowers while feeding
 Behaviour: Active during the day
 Interaction: Helps plants reproduce; competes with other pollinators

The bee’s niche is not just living in a meadow. It includes pollinating flowers, collecting
nectar, and interacting with plants and other insects.

Example 2: Owl’s Niche

 Habitat: Forests, grasslands

 Food: Hunts mice, small birds, insects
 Role: Predator (keeps rodent population in check)
 Behaviour: Nocturnal (hunts at night)
 Interaction: Competes with other night predators like foxes

Why is a Niche Important?

 It helps avoid competition – each species has its unique niche.

  It maintains balance in the ecosystem – all organisms play a role.
 If two species have the same niche, one will eventually outcompete the other (this is
called the Competitive Exclusion Principle).

Niche vs. Habitat

Term Meaning Example (Frog)

Habitat The place where an organism lives Pond

Niche The role the organism plays in the habitat Eats insects, hides from predators, lays eggs

Biosphere, Atmosphere, Lithosphere, and Hydrosphere

These four are the main components of the Earth’s system, and they all interact with each
other to support life on Earth.

BIOSPHERE – The Living World

Definition:
The biosphere is the global sum of all living things. The biosphere is the part
of Earth where life exists. It includes all living organisms—plants, animals,
fungi, bacteria, and humans.

Components:

 All ecosystems (forests, oceans, deserts, grasslands)

 All living organisms
 Thin layer of life on land, water, and air

Example:

 A forest full of trees, birds, insects, and animals

 Coral reefs in oceans with fish, algae, and coral
 Soil microbes helping plants grow

ATMOSPHERE – The Air Around Earth

Definition:

The atmosphere is the layer of gases that surrounds the Earth. It protects life and makes
weather and climate possible. The atmosphere is the Earth’s protective air blanket.

Layers of the Atmosphere:

1. Troposphere

 Altitude: 0 to ~8–15 km (varies with location and season)

 Temperature: Decreases with altitude
 Key Features:
o Where weather happens (clouds, rain, storms)
o Contains most of the atmosphere's mass (about 75–80%)
o Ends at the tropopause

2. Stratosphere

 Altitude: ~15 to 50 km
 Temperature: Increases with altitude (due to ozone absorption of UV radiation)
 Key Features:
o Contains the ozone layer
o Commercial jets often fly here (above turbulence)
o Ends at the stratopause

3. Mesosphere

 Altitude: ~50 to 85 km
 Temperature: Decreases with altitude (coldest layer)
 Key Features:
 o Meteors burn up here
o Difficult to study—too high for planes, too low for satellites
o Ends at the mesopause

4. Thermosphere

 Altitude: ~85 to 600 km (varies)

 Temperature: Increases significantly with altitude (can exceed 2,000°C or more)
 Key Features:
o Contains auroras (Northern and Southern Lights)
o The International Space Station (ISS) orbits in this layer
o Air is very thin

5. Exosphere

 Altitude: ~600 km to ~10,000 km (gradually fades into space)

 Temperature: Very high, but not "hot" in the usual sense due to sparse particles
 Key Features:
o Outermost layer
o Particles can escape into space
o Mainly hydrogen and helium

Important Gases:

 Nitrogen (78%)
 Oxygen (21%)
 Others: CO₂, Argon, water vapour

Functions:

 Supports respiration
 Protects from harmful solar radiation
 Regulates temperature
 Drives weather systems

HYDROSPHERE – The Water World

Definition:

The hydrosphere is the Earth’s water system. The hydrosphere includes all water on
Earth—in any form (liquid, solid, or gas).

Components:

 Oceans and seas

 Rivers and lakes
 Glaciers, ice caps, and icebergs
 Groundwater (under the Earth's surface)
 Water vapour in the atmosphere
Forms of Water:

 Liquid – rivers, oceans

 Solid – ice, snow
 Gas – water vapour in the air

Importance:

 Needed for life and agriculture

 Regulates climate
 Helps shape landforms (via erosion)
 Supports marine ecosystems

LITHOSPHERE – The Solid Earth

Definition:

The lithosphere is the rigid, outermost shell of the Earth. It includes the crust and the upper
part of the mantle. The lithosphere is the Earth’s solid land surface and underground
layers.

Components:

 Continents
 Mountains, valleys
 Soil and rocks
 Ocean floors

Layers:

 Crust – Earth’s outer skin

 Upper mantle – just below the crust

Importance:

 Provides soil for plants

 Contains minerals, fossil fuels, and resources
 Forms the foundation for buildings and life

How These Four Spheres Interact: They don’t exist in isolation. They interact all the time:

Example: A volcanic eruption

 Lithosphere: Volcano erupts from Earth's crust

 Atmosphere: Releases gases and ash into the air
 Hydrosphere: Lava may reach the ocean
 Biosphere: Affects plants, animals, and people nearby
 Biosphere All living organisms Life

Atmosphere Layers of gases around Earth Air

Hydrosphere All water on Earth (liquid, solid, gas) Water

Lithosphere Earth’s solid surface (land, rocks, crust) Land/Soil

Factors Affecting the Environment

There are two main types:

1. Natural Factors (Non-Human Causes)

These are environmental changes that happen on their own, through natural processes.
Examples:

a. Natural Disasters

 Volcanoes, earthquakes, tsunamis, floods, and hurricanes

 Can destroy habitats, pollute water, and change landscapes

b. Climate and Weather

 Rainfall, temperature, and winds affect ecosystems

 Droughts can dry out rivers, while heavy rains can cause floods

c. Wildfires

 Naturally caused by lightning or dry heat

 Burn forests but can also help some plants grow by clearing dead material

d. Diseases

 Outbreaks (like plant or animal diseases) can disturb population balance

2. Human Factors (Caused by People)

These are the main causes of modern environmental problems.

Examples:

a. Deforestation

 Cutting down forests for wood, farming, or building

 Leads to loss of biodiversity, soil erosion, and climate imbalance

b. Pollution
  Air pollution: From factories, vehicles
 Water pollution: From sewage, chemicals, oil spills
 Land pollution: Garbage, plastic waste
 Harms animals, plants, and human health

c. Urbanization

 Building cities and roads leads to loss of green spaces and wildlife habitat

d. Industrialization

 Increases energy use and emissions of harmful gases like CO₂ and methane
 Leads to global warming and acid rain

e. Overpopulation

 More people means more demand for food, water, housing, and energy
 Causes resource depletion and waste increase

f. Overuse of Natural Resources

 Mining, overfishing, and excessive farming damage ecosystems

g. Climate Change

 Caused mainly by greenhouse gas emissions

 Leads to melting glaciers, rising sea levels, and extreme weather

h. Agriculture and Pesticides

 Use of chemical fertilizers and pesticides can pollute soil and water

Consequences of These Factors:

 Loss of biodiversity (extinction of species)

 Global warming and climate change
 Air, water, and soil pollution
 Depletion of natural resources
 Health problems in humans
 Imbalance in ecosystems

Sources of Energy
Energy refers to all the natural sources and forms of energy that exist around us and are used by
living organisms and ecosystems. Energy sources are natural resources or man-made systems we
use to generate power for: Lighting, Cooking, Transportation, Industries, Electronics.

Types of energy sources:

Sources of energy are classified as either non-renewable (like coal, oil, and natural gas, which
will eventually run out) or renewable (like solar, wind, hydropower, biomass, and
geothermal, which can replenish naturally). Nuclear energy is another primary energy
source. These sources are used to generate electricity, heat, and power transportation.

Non-Renewable Energy Sources

Non-renewable sources are natural resources that do not replenish on a human timescale or
are used up faster than they can naturally regenerate. Once depleted, they are gone for good
(at least for thousands to millions of years). These sources are finite and formed over millions
of years from the remains of prehistoric plants and animals.

 Fossil Fuels:

 Coal: A solid fuel used for electricity generation and heating.

 Oil (Petroleum): Used for various energy needs, including transportation.
 Natural Gas: Primarily used for heating and electricity generation.
 Nuclear Energy: Energy released from the fission of radioactive minerals, like
uranium, for electricity generation.

Key Characteristics:

 Finite supply: Cannot be replenished within a human lifespan.

 Environmental impact: Burning fossil fuels releases greenhouse gases (e.g., CO₂),
contributing to climate change and pollution.
 High energy output: Efficient in energy production, which is why they have been
heavily relied upon.

Renewable Energy Sources

These sources are replenished naturally at a rate that allows them to be used sustainably (they
won't run out soon). These are eco-friendly (cause less pollution).

 Solar Energy: Energy from the sun's light and heat, used with solar panels to produce
electricity.
 Wind Energy: Harnessed by wind turbines to generate electricity.
 Hydropower: Energy from water, often from dams, used for electricity.
 Geothermal Energy: Heat from the Earth's interior.
 Biomass: Energy derived from organic materials, such as wood.
 Ocean Energy: Includes tidal energy and wave energy.

Source Description Uses

Solar Energy Energy from the sun’s rays Solar panels for homes, heating water

Wind Energy Energy from moving air Wind turbines to produce electricity

Energy from flowing water (dams, Generating electricity in hydroelectric

Hydropower
rivers) plants

Biomass Energy from organic materials (wood, Cooking, heating, producing biogas
 Source Description Uses

crop waste, dung)

Geothermal Heating homes, generating electricity in

Energy from heat inside the Earth
Energy volcanic areas

Advantages of Renewable Energy:

 Never runs out

 Low or no pollution
 Sustainable for the future

Disadvantages:

 May depend on weather (e.g., sun or wind)

 Expensive initial setup
 Not available everywhere equally

2. Non-Renewable Sources of Energy

These are sources that:

 Are limited in quantity

 Take millions of years to form
 Cause more pollution

Source Description Uses

Formed from dead plants and animals under

Fossil Fuels Electricity, transport, industry
Earth's crust

Coal Black rock, burned for power Power plants, factories

Oil (Petroleum) Liquid fossil fuel Petrol, diesel, plastics

Natural Gas Gas fossil fuel Cooking gas (LPG), electricity

Nuclear Nuclear power plants for

Comes from splitting uranium atoms
Energy electricity

Advantages:

 High energy output

 Easy to transport and use
 Infrastructure already in place

Disadvantages:

 Pollution (air, water, land)

  Greenhouse gases (cause global warming)
 Non-renewable (will run out)
 Risk of nuclear accidents (e.g., Chernobyl)

Comparison of Renewable Sources and non-renewable resources

Basis Non-Renewable Renewable

Availability Limited/fixed supply Naturally replenished
Examples Coal, oil, gas, uranium Solar, wind, hydro, biomass
Pollution High (CO₂, SO₂, NOx) Low or none

Sustainability Unsustainable long-term Sustainable

Why We Need to Shift to Renewable Energy:

 To reduce global warming and climate change

 To reduce air and water pollution
 To ensure energy for future generations
 To lower long-term energy costs